Storage medium and method and program for detecting track position of storage medium

ABSTRACT

According to one embodiment, a storage medium that stores position information indicating positions of a plurality of tracks in a radial direction in the tracks, wherein the position information includes: a first pattern in which a feed angle indicating a phase difference between the tracks is an angle obtained by adding a predetermined angle to +90°; a second pattern in which the feed angle is an angle obtained by adding the predetermined angle to −90°; and a third pattern in which the feed angle is the same as that of the first pattern.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2009-125983, filed May 26, 2009, theentire contents of which are incorporated herein by reference.

BACKGROUND

1. Field

One embodiment of the invention relates to a storage medium that storesposition information indicating positions of tracks in a radialdirection in the tracks and a track position detecting method of thestorage medium and a computer program product having a computer readablemedium including programmed instructions for detecting a track positionof the storage medium.

2. Description of the Related Art

In general, a storage medium, such as a hard disk drive (HDD), which hasa plurality of tracks concentrically, has a plurality of servo patternsin each track equidistantly. Each of the servo patterns indicates aposition in the radial direction of the track. A storage device, such asa personal computer (PC), which has the storage medium, controls a headusing a voice coil motor (VCM) control and reads the servo pattern todetect a position of the track. By detecting the position of the track,a head position in the track can be detected and the head can move to atarget track. For example, the servo pattern has four burst signal areaswhere burst signals are read by the head. Since in the servo pattern thefour burst signal areas are used to detect the position of the track inthe radial direction, the length of the servo pattern (length of acircumferential direction in the storage medium) is long.

As related technologies, a technology for increasing an informationstorage capacity of a storage medium and a technology for improvingflatness of a storage medium are provided (for example, Japanese PatentApplication Publication (KOKAI) No. 2000-90609, Japanese PatentApplication Publication (KOKAI) No. 2006-120299, and Japanese PatentApplication Publication (KOKAI) No. 2008-171513).

A storage area where user data is stored is provided between adjacentservo patterns. For this reason, when the length of the servo pattern islong, the storage area of the user data is narrowed and the storagecapacity is reduced.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

A general architecture that implements the various features of theinvention will now be described with reference to the drawings. Thedrawings and the associated descriptions are provided to illustrateembodiments of the invention and not to limit the scope of theinvention.

FIG. 1 is an exemplary view of a servo pattern of a storage mediumaccording to an embodiment of the invention;

FIG. 2 is an exemplary view of a format configuration of the servopattern in the storage medium in the embodiment;

FIG. 3 is an exemplary diagram of position areas in the embodiment;

FIG. 4 is an exemplary view of signal patterns of the position areaseven1 and even2 to which dithering is not applied;

FIG. 5 is an exemplary view of signal patterns of position areas even1and even2 to which dithering is applied in the embodiment;

FIG. 6A is an exemplary graph illustrating a relationship between anactual cylinder position and a demodulation position, when dithering isnot applied to each position area;

FIG. 6B is an exemplary graph illustrating a relationship between anactual cylinder position and a demodulation position, when dithering isapplied to each position area in the embodiment;

FIG. 7 is an exemplary view of a signal pattern of a position area odd1to which dithering is applied in the embodiment;

FIG. 8 is an exemplary block diagram of a storage device that has thestorage medium in the embodiment;

FIG. 9 is an exemplary functional block diagram of the storage devicethat has the storage medium in the embodiment;

FIG. 10 is an exemplary flowchart of processes in a track positiondetecting method of the storage medium in the embodiment;

FIG. 11 is an exemplary diagram of a demodulating process in theembodiment;

FIG. 12 is an exemplary diagram of another odd demodulating method inthe embodiment;

FIG. 13 is an exemplary view of a mirror image of a vector in theembodiment;

FIG. 14A is an exemplary view of rotation of an odd vector by a firstsynthesis in the embodiment;

FIG. 14B is an exemplary view of a first synthesis result in theembodiment;

FIG. 15A is an exemplary view of an odd demodulation result with respectto an angle in the embodiment;

FIG. 15B is an exemplary view of a fine demodulation result with respectto the angle in the embodiment;

FIG. 15C is an exemplary view of a result with respect to the angle thatis obtained by subtracting the angle indicating the fine demodulationresult from the angle indicating the odd demodulation result in theembodiment;

FIG. 16A is an exemplary view of rotation of a coarse vector by a secondsynthesis in the embodiment;

FIG. 16B is an exemplary view of a second synthesis result in theembodiment;

FIG. 17A is an exemplary view of a coarse demodulation result withrespect to an angle in the embodiment;

FIG. 17B is an exemplary view of an odd demodulation result with respectto the angle in the embodiment;

FIG. 17C is an exemplary view of a result with respect to the angle thatis obtained by subtracting the angle indicating the odd demodulationresult from the angle indicating the coarse demodulation result in theembodiment;

FIG. 18 is an exemplary diagram of position areas where a feed angle isdifferent in the embodiment;

FIG. 19 is an exemplary diagram of position areas of a storage mediumwhere technology disclosed in the present application is not applied;and

FIG. 20 is an exemplary view of a computer system where the technologydisclosed in the present application is applied.

DETAILED DESCRIPTION

Various embodiments according to the invention will be describedhereinafter with reference to the accompanying drawings. In general,according to one embodiment of the invention, a storage medium thatstores position information indicating positions of a plurality oftracks in a radial direction in the tracks, wherein the positioninformation includes: a first pattern in which a feed angle indicating aphase difference between the tracks is an angle obtained by adding apredetermined angle to +90°; a second pattern in which the feed angle isan angle obtained by adding the predetermined angle to −90°; and a thirdpattern in which the feed angle is the same as that of the firstpattern.

According to another embodiment of the invention, a track positiondetecting method of a storage medium that stores position informationindicating positions of a plurality of tracks in a radial direction inthe tracks, the track position detecting method comprising: acquiringfirst phase information from a first pattern of the position informationin which a feed angle indicating a phase difference between the tracksis an angle obtained by adding a predetermined angle to +90°; acquiringsecond phase information from a second pattern of the positioninformation in which the feed angle is an angle obtained by adding thepredetermined angle to −90°; acquiring third phase information from athird pattern of the position information in which the feed angle is thesame as that of the first pattern; and performing demodulation using thefirst, second, and third phase information to detect a position of thetrack.

According to still another embodiment of the invention, a computerprogram product having a computer readable medium including programmedinstructions for detecting a track position of a storage medium thatstores position information indicating positions of a plurality oftracks in a radial direction in the tracks, wherein the instructions,when executed by a computer, cause the computer to perform: acquiringfirst phase information from a first pattern of the position informationin which a feed angle indicating a phase difference between the tracksis an angle obtained by adding a predetermined angle to +90°; acquiringsecond phase information from a second pattern of the positioninformation in which the feed angle is an angle obtained by adding thepredetermined angle to −90°; acquiring third phase information from athird pattern of the position information in which the feed angle is thesame as that of the first pattern; and performing demodulation using thefirst, second, and third phase information to detect a position of thetrack.

One embodiment according to the invention will be described hereinafterwith reference to the accompanying drawings. FIG. 1 illustrates a servopattern of a storage medium according to the embodiment of theinvention. As illustrated in FIG. 1, in a storage medium 1, a pluralityof servo patterns 11 that extend in a radial direction from a center ofthe storage medium 1 are equidistantly provided in a circumferentialdirection by an embedded servo method, for example. In the storagemedium 1, a plurality of tracks 12 are provided concentrically, and theservo patterns 11 are stored in the tracks 12 and indicate positions ofthe tracks 12 in the radial direction. According to this configuration,a position of a head (to be descried below) on the track can be detectedby using the servo patterns 11. A storage area in which user data, forexample, is stored is provided between the adjacent servo patterns 11.The storage medium 1 has a plurality of layers laminated at a regularinterval, and the track 12 is called as a cylinder. The storage medium 1may have a single layer.

FIG. 2 illustrates a format configuration of the servo pattern in thestorage medium in the embodiment. As illustrated in FIG. 2, a format ofthe servo pattern 11 has a preamble 111, a servo mark 112, a gray code113, a position 114, post data 115, and a gap 116. The preamble 111indicates so-called a gap that separates the storage area of the userdata and the servo pattern 11. The servo mark 112 indicates a start ofthe servo pattern 11. The gray code 113 has a cylinder number and a headnumber, for example that are numerical values. The position 114 isso-called a burst signal area that has position information of thecylinder in the radial direction, which will be described in detailbelow. The post data 115 has a Repetitive Run out (RRO) correction valuethat is a numerical value. The gap 116 separates the servo pattern 11and the storage area of the user data.

The position 114 has areas indicating three burst signals that areposition areas even1, odd1, and even2 in which signal patterns arewritten, respectively. The signal patterns have phases that are read asthe burst signals by the head to be described below. When each positionarea is read by the head, the position information of the cylinder inthe radial direction can be detected. Accordingly, since the positioninformation of the cylinder in the radial direction can be detected byusing each position area, the position of the head in the cylinder canbe detected.

The position areas are be explained with reference to FIG. 3. A feedangle illustrated in FIG. 3 indicates a phase difference between thecylinders. That is, the feed angle is an angle of a phase that variesfor every cylinder in the signal pattern of each position area, and aunit thereof is deg/cyl. Because the head crosses each position area ata predetermined speed by a seek operation in which the head is moved bya VCM to be described below, a speed correction is performed to correcta variation in the angle of the phase generated due to the predeterminedspeed. V indicates a speed correction component. A time correction isperformed to correct a variation in the phase angle generated due toaccumulation of a variation in a clock needed when a Discrete FourierTransform (DFT) is performed. T indicates a time correction component.An initial phase in each position area is a. Each unit of the speedcorrection, the time correction, and the initial phase is deg.

The position area even1 has a feed angle of +101.25 deg/cyl. Thisindicates that a phase of a signal pattern becomes 0° in a cylinder 0 asa reference cylinder, a phase becomes 101.25° in a cylinder 1, and aphase becomes 202.5° in a cylinder 2. Likewise, the position area odd1has a feed angle of −78.75 deg/cyl. This indicates that a phase of asignal pattern becomes 0° in a cylinder 0 as a reference cylinder, aphase becomes −78.75° in a cylinder 1, and a phase becomes −157.5° in acylinder 2. Since the position area even2 has the same feed angle asthat of the position area even1, the description thereof will beomitted.

Each position area has the above-described feed angle. If a demodulationis performed using each position area, linearity of ±8 cylinders can beobtained. This is because, if a calculation of adding a phase of theposition area odd1 to a phase of the position area even1 or even2 isperformed by coarse demodulation to be described below, a phase of 0° iscalculated in the cylinder 0 but a phase of +101.25°+(−78.75°) iscalculated in the cylinder 1, and a phase difference of 22.5° can beobtained. If the phase of one cylinder is represented by 22.5°, thephase of 16 cylinders can be represented by 360°. As a result, aposition of a target cylinder can be detected in a wide range of ±8cylinders. Since each position area has the above-described feed angle,even though a shock is applied at a time of the seek operation withrespect to the target cylinder and variation corresponding to 8cylinders is generated in the position of the head, seek of the head tothe target cylinder is enabled.

Since each position area has the above-described feed angle, linearityof ±1 cylinder can be obtained, when the demodulation is performed usingeach position area. This is because, if a calculation of even-odd isperformed by fine demodulation to be described below, a phase of 0° iscalculated in the cylinder 0 but a phase of +101.25° -)(−78.75° iscalculated in the cylinder 1, and a phase difference of 180° can beobtained. Because the phase of one cylinder is represented by 180°, thephase of the two cylinders can be represented by 360°. As a result, theposition of the target cylinder can be detected in a fine range of ±1cylinder. The feed angles of the position areas are not limited to theabove feed angles, and may have feed angles where a difference betweenthe feed angle of each of the position areas even1 and even2 and thefeed angle of the position area odd1 becomes +180°. The feed angles ofthe position areas may have feed angles where a sum of the feed angle ofeach of the position areas even1 and even2 and the feed angle of theposition area odd1 becomes −22.5° or +22.5°

Dithering is applied to the signal pattern of each position area suchthat a demodulation position corresponding to the position of thecylinder calculated based on each phase, using a phase demodulatingmethod to be described below is similar to the actual position of thecylinder on the storage medium 1 corresponding to the demodulationposition (hereinafter, referred to as “actual cylinder position”). Byapplying the dithering, the signal pattern of each position area has azigzag pattern that has patterns of five clocks to be described below inall directions. For example, if the dithering is not applied to theposition areas even1 and even2, as illustrated in FIG. 4, discontinuousplaces 3 where the signal patterns are discontinuous are generated.Similarly, this situation is applicable to the position area odd1. Ifthe feed angle of each position area has a round number such as +90° or−90°, a pattern where a signal pattern is not discontinuous can beformed at the time of Servo track writing (STW). However, since the feedangle of each position area is +101.25° or −78.75° that is obtained byadding +11.25° or −11.25° to +90° or −90°, the signal pattern becomesdiscontinuous. The feed angles +11.25° and −11.25° are ±½ values of22.5° that is an angle to detect the position of the target cylinder inthe range of ±8 cylinders.

Meanwhile, when the dithering is applied, the signal patterns of theposition areas even1 and even2 become the state where patterns 4 of fiveclocks like 00000 or 11111 illustrated in FIG. 5 are provided in alldirections. FIG. 6A illustrates a relationship between the actualcylinder position and the demodulation position, when the dithering isnot applied to each position area. FIG. 6B illustrates a relationshipbetween the actual cylinder position and the demodulation position, whenthe dithering is applied to each position area. As illustrated in FIG.6A, when the dithering is not applied, a slope of a line indicating therelationship between the actual cylinder position and the demodulationposition varies at the discontinuous place 3. For this reason, therelationship between the actual cylinder position and the demodulationposition does not become linearity but becomes so-called non-linearity(position non-linearity). Meanwhile, as illustrated in FIG. 6B, when thedithering is applied, the relationship between the actual cylinderposition and the demodulation position becomes approximately linearity,and linearity can be (position linearity) can be obtained.

The position areas even1 and even 2 are described above, but thedithering is similarly applied to the position area odd1. FIG. 7illustrates a signal pattern of the position area odd1 to which thedithering is applied. As illustrated in FIG. 7, the signal pattern ofthe position area odd1 also has patterns 4 of five clocks in alldirections. In the above cases, the signal pattern of each position areahas the patterns 4 of five clocks, but the invention is not limitedthereto. For example, the signal pattern of each position area may havepatterns of the number of clocks such that the relationship between theactual cylinder position and the demodulation position becomeslinearity.

Next, a track position detecting method executed by a storage devicehaving the storage medium according to the embodiment will be described.FIG. 8 is a block diagram of a storage device having the storage medium.As illustrated in FIG. 8, a storage device 5 includes the storage medium1, a spindle motor (SPM) 51, a head actuator 52, a VCM 53, a head 54,and a controller 55.

The SPM 51 rotationally drives the storage medium 1. The head actuator52 is an arm that is disposed on the VCM 53 and supports the head 54held on an end of the head actuator 52. The VCM 53 drives the headactuator 52 and performs seek of the head 54, and so on. The head 54acquires phase information from each position area in the storage medium1, reads data stored in the storage medium 1, and writes data into thestorage medium 1. The controller 55 performs SPM control to control theSPM 51 and VCM control to control the VCM 53, and executes the trackposition detecting method to be described below. The controller 55 has adriving circuit 551, a preamplifier 552, a read/write channel (RDC) 553,a central processing unit (CPU) 554, a memory 555, a hard diskcontroller (HDC) 556, and a buffer 557.

The driving circuit 551 rotationally drives the SPM 51 and drives theVCM 53. The preamplifier 552 amplifies a signal read from the storagemedium 1 by the head 54 and a signal written in the storage medium 1 bythe head 54. The RDC 553 encodes information to be written in thestorage medium 1 and decodes a signal that is read from the storagemedium 1.

The CPU 554 controls the operations of the above configuration, and thememory 555 is a rewritable nonvolatile storage medium that storesprograms and data, and so on. The HDC 556 corrects an error of datatransmitted and received between the storage device 5 and an externaldevice such as a host. The buffer 557 temporarily stores data tocompensate for variation in timing of data input/output processing,generated when the data is transmitted and received between the HDC 556and the external device.

FIG. 9 illustrates a functional block of the storage device that has thestorage medium in the embodiment. As illustrated in FIG. 9, the storagedevice 5 has a driver 501 that rotationally drives the SPM 51 and drivesthe VCM, an acquiring module 502 that acquires the phase information asa vector by reading each position area, and a processor 503 thatexecutes a phase demodulating process and a synthesizing process to bedescribed below, based on the acquired vector, and detects the positionof the cylinder. The above mentioned individual functions in the storagedevice 5 are realized when the CPU 554 reads the program stored in thememory 555 and the CPU 554 and the memory 555 cooperate with each other.

FIG. 10 is a flowchart of a track position detecting processing of thestorage medium in the embodiment. First, if an instruction indicatingthat the position of the cylinder needs to be detected to read or writedata, and so on is input to the storage device 5 by a user, the driver501 starts to rotationally drive the SPM 51 and drive the VCM 53 withthe driving circuit 551 (S101). After the driving starts, the acquiringmodule 502 acquires the phase information as the vector from eachposition area with the head 54 (S102). After the acquisition, theprocessor 503 executes the phase demodulating process based on the phaseinformation (S103). After the phase demodulating process, the processor503 executes the synthesizing process on the result of the phasedemodulating process (S104). After the synthesizing process, theprocessor 503 detects the position of the cylinder based on the resultsof the phase demodulating process and the synthesizing process (S105),and this flow ends.

FIG. 11 illustrates the phase demodulating process. In FIG. 11, evenindicates the vector of the position areas even1 and even2, and oddindicates the vector of the position area odd 1. The phase demodulatingprocess is executed in the order of the fine demodulation, odddemodulation, and the coarse demodulation. The fine demodulationperforms a calculation of even−odd, and its demodulation gain is 180deg/cyl and its repetition cycle is 2 cyl. That is, the phase differenceof 180° is obtained for each cylinder. For this reason, the phasedifference of 360° is obtained by two cylinders. By this configuration,the position of the target cylinder can be detected in the range of ±1cylinder. The odd demodulation performs a calculation of[(even+odd)/2]+odd, and its demodulation gain is 90 deg/cyl and itsrepetition cycle is 4 cyl. That is, the phase difference of 90° isobtained for each cylinder. For this reason, the phase difference of360° is obtained by four cylinders. By this configuration, the positionof the target cylinder can be detected in a range of ±2 cylinders. Thecoarse demodulation performs a calculation of even+odd, and itsdemodulation gain is 22.5 deg/cyl and its repetition cycle is 16 cyl.That is, the phase difference of 22.5° is obtained for each cylinder.For this reason, the phase difference of 360° is obtained by sixteencylinders. By this configuration, the position of the target cylindercan be detected in the range of ±8 cylinders.

In this case, since the odd demodulation includes the coarsedemodulation, the processor 503 performs the coarse demodulation beforeperforming the odd demodulation, and performs the coarse demodulationagain thereafter. Instead of performing the coarse demodulation again,the result of the temporary coarse demodulation may be used. In thiscase, the correction may be performed on the odd without performing thecoarse demodulation before performing the odd demodulation, and the odddemodulation may be performed.

FIG. 12 illustrates another odd demodulating method. A correctionillustrated in the calculation principle of the odd demodulationincludes a correction using the gray code 113 and a correction using anestimation position. The estimation position indicates an estimatedposition of a cylinder where a vector is acquired, and is obtained byestimating the cylinder where the head 54 is positioned. The correctionusing the gray code 113 is a correction that enables acquisition of thesame result as even+odd by applying 11.25° to a value of the cylindernumber, because the cylinder number indicated by the gray code 113increases by 1 for every cylinder. The correction using the estimationposition is a correction that applies 11.25° to the cylinder numberindicating the cylinder estimated as the cylinder where the head 54 ispositioned, similar to the correction using the gray code 113.

The processor 503 performs a calculation using a mirror image of odd,such as odd reversely rotates, when the coarse demodulation isperformed. That is, the processor 503 inverts the polarity of odd. Thisreason is as follows. In the vector addition of even+odd in the coarsedemodulation, the vector length varies, and it is difficult to get astable phase, when the synthesis vector is used. FIG. 13 illustrates amirror image of a vector. As illustrated in FIG. 13, in order to use avector 61 as a mirror vector 62 with respect to a reference line 6, theprocessor 503 sets Y′=−Y and inversely transform a Y axis component. Inthis way, the vector 61 becomes the mirror vector 62 having a reverserotation direction. As a method that reversely rotates odd other thanY′=−Y, any one of X′=−X, X′=Y, and Y′=X maybe used. Alternatively, evenmay be reversely rotated, instead of reversely rotating odd.

Next, the synthesizing process will be described. In the synthesizingprocess, the processor 503 performs a first synthesis that is asynthesis of a vector calculated by the odd demodulation and a vectorcalculated by the fine demodulation. After the first synthesis, theprocessor 503 performs a second synthesis that is a synthesis of avector calculated by the coarse demodulation and a vector calculated bythe fine demodulation or a vector calculated by the odd demodulation.The first synthesis is explained using the vectors calculated by thedemodulations with reference to FIGS. 14A and 14B. As illustrated inFIG. 14A, the processor 503 sets a value of ½ of an angle of the vectorcalculated by the fine demodulation as a rotation operator and rotatesan odd demodulation vector 71 calculated by the odd demodulation usingthe rotation operator. Thereby, as illustrated in FIG. 14B, a judgingmethod using two quadrature vectors that separates the odd demodulationvector 71 into vectors in two quadratures of 0° and 180° is enabled, andthe position of the target cylinder can be detected with precision in arange of ±2 cylinders. In FIG. 14B, a state where the first synthesis isperformed a plurality of times is illustrated. In a first synthesisvector 711 obtained as the result of the first synthesis, angledifferences exist in the two quadratures. This is because errors aregenerated in the angles of the first synthesis vector 711, even thoughthe first synthesis is performed. However, even though the errors aregenerated, since the odd demodulation vector 71 is separated into anglesapproximated to 0° and 180°, the position of the target cylinder can bedetected with precision in the range of ±2 cylinders.

The first synthesis is explained using angles calculated by thedemodulations with reference to FIGS. 15A to 15C. In FIG. 15A, 72denotes a value obtained by representing the vector calculated by theodd demodulation by the angle. In FIG. 15B, 73 denotes a value obtainedby representing the vector calculated by the fine demodulation by theangle. S0 to S10 illustrated in FIGS. 15A to 15C denote the cylindernumbers. An angle 72 becomes 360° by four cylinders and an angle 73becomes 360° by two cylinders. If the angle 73 is subtracted from theangle 72, as illustrated in FIG. 15C, each cylinder can be illustratedby the two angles of 0° and 180°. By the first synthesis, since unwantedangles other than 0° and 180° are removed, the position of the targetcylinder can be detected with precision in the range of ±2 cylinders.

The second synthesis is explained using the vectors calculated by thedemodulations with reference to FIGS. 16A and 16B. As illustrated inFIG. 16A, the processor 503 sets a value of ½ of an angle of the vectorcalculated by the odd demodulation or a value of ¼ of an angle of thevector calculated by the fine demodulation as a rotation operator androtates a coarse demodulation vector 81 calculated by the coarsedemodulation using the rotation operator. Thereby, as illustrated inFIG. 16B, a judging method using four quadrature vectors that separatesthe coarse demodulation vector 81 into vectors in four quadratures of45°, 135°, −45°, and −135° is enabled. In FIG. 16B, a state where thesecond synthesis is performed a plurality of times is illustrated. In asecond synthesis vector 811 obtained as the result of the secondsynthesis, angle differences exist in each quadrature. This is becauseerrors are generated in the angles of the second synthesis vector 811,even though the second synthesis is performed. However, even though theerrors are generated, since the coarse demodulation vector 81 isseparated into angles approximated to 45°, 135°, −45°, and −135°, theposition of the target cylinder can be detected with precision in arange of ±8 cylinders.

The second synthesis is explained using angles calculated bydemodulations with reference to FIGS. 17A to 17C. In FIG. 17A, 82denotes a value obtained by representing the vector calculated by thecoarse demodulation by the angle. In FIG. 17B, 83 denotes a valueobtained by representing the vector calculated by the odd demodulationby the angle. S0 to S16 illustrated in FIGS. 17A to 17C denote thecylinder numbers. An angle 82 becomes 360° by sixteen cylinders and anangle 83 becomes 360° by four cylinders. If the angle 83 is subtractedfrom the angle 82, as illustrated in FIG. 17C, each cylinder can beillustrated by the four angles of 45°, 135°, 225° or −135°, and 315° or−45°. By the second synthesis, since unwanted angles other than 45°,135°, −45°, −135° are removed, the position of the target cylinder canbe detected with precision in the range of ±8 cylinders.

According to the first synthesis and the second synthesis, since thejudging method using two quadrature vectors and the judging method usingfour quadrature vectors are used to detect the position of the targetcylinder in the range of ±2 cylinders and the range of ±8 cylinders,calculations of a plurality of times using an arc tan function do notneed to be performed. As a result, load on the CPU 554 can be reduced.

In the embodiment, the synthesizing process of S104 is executed afterthe demodulating process of S103 is executed. However, the firstsynthesis may be performed after the odd demodulation in thedemodulating process. In the embodiment, the feed angle of each positionarea is the feed angle illustrated in FIG. 3. However, as illustrated inFIG. 18, the values of the position areas even1, even2 and the value ofthe position area odd1 may be replaced.

As a comparative example, position areas of a storage medium to whichthe technology disclosed in the present application is not applied willbe described. FIG. 19 is an exemplary view of position areas of thestorage medium to which the technology disclosed in the presentapplication is not applied. As illustrated in FIG. 19, unlike thestorage medium 1 in the embodiment, the storage medium in thecomparative example has a position area odd2. For this reason, in thestorage medium in the comparative example, the width of the servopattern is wider than that of the storage medium 1, and a storage areaof the user data is narrowed. In addition, operations of the speedcorrection and the time correction need to be performed on the positionarea odd2. As a result, in the storage medium in the comparativeexample, the load on the CPU 554 is larger than that of the storagemedium 1.

Meanwhile, according to the embodiment, since the position of the targetcylinder is detected using the three position areas, the length of theservo pattern can be decreased. Consequently, the storage capacity ofthe user data can be increased. In the storage medium in the comparativeexample, even though the demodulation is performed based on threeposition areas of even1′, odd1′, and even2′, the position of the targetcylinder cannot be detected in the range of ±8 cylinders. Meanwhile,according to the embodiment, if the position of the target cylinder isdetected using the three position areas, the position of the targetcylinder can be detected in the range of ±8 cylinders. According to theembodiment, the position of the target cylinder can be detected in therange of ±1 cylinder and the range of ±2 cylinders.

The technology disclosed in the present application can be applied to acomputer system to be described below. FIG. 20 is an exemplary view of acomputer system where the technology disclosed in this application isapplied. A computer system 920 illustrated in FIG. 20 has a main body901 where a CPU or a hard disk drive is embedded, a display 902 thatdisplays an image according to an instruction from the main body 901, akeyboard 903 that is used to input a variety of information to thecomputer system 920, a mouse 904 that is used to designate an arbitraryposition on a display screen 902 a of the display 902, and acommunication device 905 that has access to an external database anddownloads a program stored in another computer system. The communicationdevice 905 may be a network communication card or a modem.

In the computer system that constitutes the storage device having thestorage medium 1, a program for executing the steps above mentioned canbe provided as a track position detecting program. This program can bestored in a storage medium that is readable by the computer system andcan be executed by the computer system that constitutes the storagedevice having the storage medium 1. The program for executing the stepsis stored in a portable storage medium such as a disk 910 or downloadedfrom a storage medium 906 of another computer system through thecommunication device 905. A track position detecting program (or trackposition detecting software) that causes the computer system 920 to haveat least a track position detecting function is input to the computersystem 920 to be compiled. This program causes the computer system 920to be operated as a storage device having the track position detectingfunction. This program may be stored in a computer readable storagemedium such as the disk 910.

Examples of the storage medium that is readable by the computer system920 comprise an internal storage device embedded in a computer such as aROM or a RAM, the disk 910 or a flexible disk, a DVD disk, amagneto-optical disk, a portable storage medium such as an IC card, adatabase storing a computer program, another computer system and adatabase thereof, and various storage media that can be accessed by acomputer system connected through a communication module such as thecommunication device 905.

Position information corresponds to the position 114 and a predeterminedangle corresponds to +11.25° or −11.25°. A first pattern corresponds tothe position area even1, a second pattern corresponds to the positionarea odd1, and a third pattern corresponds to the position area even2. Afirst range corresponds to the range of ±1 cylinder and a second rangecorresponds to the range of ±8 cylinder.

The various modules of the systems described herein can be implementedas software applications, hardware and/or software modules, orcomponents on one or more computers, such as servers. While the variousmodules are illustrated separately, they may share some or all of thesame underlying logic or code.

While certain embodiments of the inventions have been described, theseembodiments have been presented by way of example only, and are notintended to limit the scope of the inventions. Indeed, the novel methodsand systems described herein may be embodied in a variety of otherforms; furthermore, various omissions, substitutions and changes in theform of the methods and systems described herein may be made withoutdeparting from the spirit of the inventions. The accompanying claims andtheir equivalents are intended to cover such forms or modifications aswould fall within the scope and spirit of the inventions.

1. A storage medium configured to store position information indicatingpositions of a plurality of tracks in a radial direction in the tracks,wherein the position information comprises: a first pattern in which afeed angle indicating a phase difference between the tracks is obtainedby adding a predetermined angle to +90°; a second pattern in which thefeed angle is obtained by adding the predetermined angle to −90°; and athird pattern in which the feed angle is the same as the feed angle ofthe first pattern.
 2. The storage medium of claim 1, wherein ditheringis applied to the first pattern, the second pattern, and the thirdpattern in such a manner that a position of the track calculated basedon phases of the first pattern, the second pattern, and the thirdpattern is substantially the same as an actual track positioncorresponding to the calculated track position.
 3. The storage medium ofclaim 1, wherein a phase difference between a phase of the first patternor the third pattern and a phase of the second pattern indicates aposition of the track in the radial direction in a first range of apredetermined number of tracks, and a phase difference between the phaseof the first pattern or the third pattern and a phase in which apolarity of the second pattern is reversed or a phase difference betweena phase in which a polarity of the first pattern or the third pattern isreversed and the phase of the second pattern indicates a position of thetrack in the radial direction in a second range wider than the firstrange.
 4. The storage medium of claim 1, wherein a difference betweenthe feed angle of each of the first pattern and the third pattern andthe feed angle of the second pattern is +180°, and a sum of the feedangle of each of the first pattern and the third pattern and the feedangle of the second pattern is −22.5° or +22.5°.
 5. The storage mediumof claim 1, wherein the predetermined angle is +11.25° or −11.25°.
 6. Atrack position detecting method of a storage medium configured to storeposition information indicating positions of a plurality of tracks in aradial direction in the tracks, the track position detecting methodcomprising: acquiring first phase information from a first pattern ofthe position information in which a feed angle indicating a phasedifference between the tracks is obtained by adding a predeterminedangle to +90°; acquiring second phase information from a second patternof the position information in which the feed angle is obtained byadding the predetermined angle to −90°; acquiring third phaseinformation from a third pattern of the position information in whichthe feed angle is the same as the feed angle of the first pattern; anddemodulating the first, second, and third phase information in order todetect a position of the track.
 7. The track position detecting methodof claim 6, wherein the position of the track in the radial direction ina first range of a predetermined number of tracks is detected based onthe demodulation of the first phase information or the third phaseinformation and the second phase information, and the position of thetrack in the radial direction in a second range wider than the firstrange is detected based on the demodulation of the first phaseinformation or the third phase information and information in which apolarity of the second phase information is reversed, or thedemodulation of information in which a polarity of the first phaseinformation is reversed or information in which a polarity of the thirdphase information is reversed and the second phase information.
 8. Thetrack position detecting method of claim 6, wherein the demodulationusing the first phase information, the second phase information, and thethird phase information comprises: fine demodulation to calculate aphase difference between the first phase information or the third phaseinformation and the second phase information as a first vector; odddemodulation to calculate a second vector by performing predeterminedcorrection on the second phase information; and coarse demodulation tocalculate a phase difference between the first phase information or thethird phase information and information in which a polarity of thesecond phase information is reversed or a phase difference betweeninformation in which a polarity of the first phase information isreversed or information in which a polarity of the third phaseinformation is reversed and the second phase information as a thirdvector.
 9. The track position detecting method of claim 8, wherein thepredetermined correction uses at least one of the third vector, a graycode in the position information, and an estimation position indicatingan estimated position of the track from which the first phaseinformation, the second phase information, and the third phaseinformation are acquired.
 10. The track position detecting method ofclaim 8, wherein a ½ value of an angle in the first vector is used as afirst rotation operator, and the second vector is rotated using thefirst rotation operator.
 11. The track position detecting method ofclaim 8, wherein a ½ value of an angle in the second vector or a ¼ valueof an angle in the first vector is used as a second rotation operator,and the third vector is rotated using the second rotation operator. 12.A computer program product having a computer readable medium includingprogrammed instructions for detecting a track position of a storagemedium configured to store position information indicating positions ofa plurality of tracks in a radial direction in the tracks, wherein theinstructions, when executed by a computer, cause the computer toperform: acquiring first phase information from a first pattern of theposition information in which a feed angle indicating a phase differencebetween the tracks is obtained by adding a predetermined angle to +90°;acquiring second phase information from a second pattern of the positioninformation in which the feed angle is obtained by adding thepredetermined angle to −90°; acquiring third phase information from athird pattern of the position information in which the feed angle is thesame as the feed angle of the first pattern; and demodulating the first,second, and third phase information to detect a position of the track.13. The computer program product of claim 12, wherein the position ofthe track in the radial direction in a first range of a predeterminednumber of tracks is detected based on the demodulation of the firstphase information or the third phase information and the second phaseinformation, and the position of the track in the radial direction in asecond range wider than the first range is detected based on thedemodulation of the first phase information or the third phaseinformation and information in which a polarity of the second phaseinformation is reversed, or the demodulation of information in which apolarity of the first phase information is reversed or information inwhich a polarity of the third phase information is reversed and thesecond phase information.
 14. The computer program product of claim 12,wherein the demodulation of the first phase information, the secondphase information, and the third phase information comprises: finedemodulation to calculate a phase difference between the first phaseinformation or the third phase information and the second phaseinformation as a first vector; odd demodulation to calculate a secondvector by performing predetermined correction on the second phaseinformation; and coarse demodulation to calculate a phase differencebetween the first phase information or the third phase information andinformation in which a polarity of the second phase information isreversed or a phase difference between information in which a polarityof the first phase information is reversed or information in which apolarity of the third phase information is reversed and the second phaseinformation as a third vector.
 15. The computer program product of claim14, wherein the predetermined correction is configured to use at leastone of the third vector, a gray code in the position information, and anestimation position indicating an estimated position of the track fromwhich the first phase information, the second phase information, and thethird phase information are acquired.
 16. The computer program productof claim 14, wherein a ½ value of an angle in the first vector is usedas a first rotation operator, and the second vector is rotated using thefirst rotation operator.
 17. The computer program product of claim 14,wherein a ½ value of an angle in the second vector or a ¼ value of anangle in the first vector is used as a second rotation operator, and thethird vector is rotated using the second rotation operator.